21078225 has 60 divisors (see below), whose sum is σ = 44651904. Its totient is φ = 9629280.

The previous prime is 21078209. The next prime is 21078257. The reversal of 21078225 is 52287012.

It is not a de Polignac number, because 21078225 - 2⁴ = 21078209 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 13432 + ... + 14918.

Almost surely, 2^21078225 is an apocalyptic number.

21078225 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21078225 is an abundant number, since it is smaller than the sum of its proper divisors (23573679).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21078225 is a wasteful number, since it uses less digits than its factorization.

21078225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1516 (or 1502 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21078225 is about 4591.1028086942. The cubic root of 21078225 is about 276.2345595814.

The spelling of 21078225 in words is "twenty-one million, seventy-eight thousand, two hundred twenty-five".